Carbon fiber reinforced plastic (CFRP) components are nowadays used in many industrial fields, e.g., in the aeronautic and automobile industry, as they enable a significant weight reduction compared to previously used metal parts and provide sufficient stability and therefore safety for the user.
During production of CFRP components carbon fibers are suspended in resin and then hardened. After hardening the CFRP components often are further treated, e.g., by grinding, cutting, sharpening, forming, etc. However, during these further treatments or already during the production of the CFRP components normally defects occur on the surface thereof, e.g., places where carbon fibers are at least partially exposed to the surroundings.
If such places with defects are then bound to a metal in a hybrid structure in e.g., airplanes, cars, bikes, etc. and water is present or gets to the binding location between an exposed carbon fiber part and the metal, a galvanic cell may be formed, which may lead to rusting of the metal due to the reduction of oxygen on the carbon fiber.
To avoid the formation of a galvanic cell it is therefore necessary to repair those surface defects, e.g., at edges, but also pores formed during the CFRP component production and to insulate the CFRP component.
Conventionally this repairing of defects is either carried out manually, which requires a lot of time and labor and is thus time- and cost-extensive, or is done by extensive application of isolating glass plies, resin layers or coatings, using e.g., epoxy resin or polyurethane resin, which is costly and requires a significant amount of material.
It is also known to use electrodeposition coating for composite components after a previous metallization of the components for different purposes. However, also such treatment leads to an increase in weight of the CFRP component and thus is not advantageous, especially in light-weight applications. Also this electrodeposition coating after metallization does not target the electrical insulation of the composite component in order to avoid the formation of galvanic cells and therefore corrosion in CFRP/metal hybrid structures.
A conventional electrophoretic deposition process is known from WO 95/23246, according to which a defect-free metallic oxide coating can be deposited on a substrate.